Generating spatially variable phase shift map between two stack volumes
The automatic mistie correction tool outputs a singular time shift and phase shift value.
While the cross correlation process (LINK) is able to output a spatially varying time shift map based on best resulting correlation (in header), it does not output a phase shift map.
The two workflows below outline the steps to generate phase shift maps based on peak amplitude time shift maps in order to quantify phase and time differences between input traces for data analysis and QC.
Workflow 1: Automatic mapping of phase shift at peak amplitude time shift [Require Image Gather Processing License Module]
- Use the cross correlation process to output a correlogram between two stack volumes within a defined vertical window.
- Use Instantaneous attribute to produce instantaneous amplitude and instantaneous phase volumes .
- Map peak amplitude time to a header using attribute maps. Assign it to any header (e.g 99 sstat: Source Static Correction). This will be the time shift map based on peak amplitude.
- Volume: Instantaneous attribute: Amplitude
- Attribute source: calculate from sample
- Primary output to: Set header in process output
- Set attribute to peak (time/depth).
Note: Some headers (eg: sstat) will have a precision up to 1ms and will round the value up while other headers have higher precision levels ( eg: gx up to 2 decimal points).
Extracted time shift header, sstat can be viewed on section and header axis.
- Map the time shift value (sstat header) to the phase attribute volume using volume maths simple.
Note that this process will only transfer the sstat header to the instantaneous attribute:phase volume. The sample values of the instantaneous phase volume will remain the same.
- Extract phase shift value at peak amplitude time using header maths operation using the formula sample(sstat) and store the information in a header. Assign it to any appropriate header (e.g 101 gstat: Group Static Correction).
Extracted phase shift header values, gstat can be viewed on section and header axis.
- The phase shift and time shift (based on peak amplitude) map can be viewed using attribute maps.
Workflow 2: Manual mapping of phase shift at peak amplitude time shift
- Use the cross correlation process to output a correlogram between two stack volumes within a defined vertical window
- Use Instantaneous attribute to produce instantaneous amplitude and instantaneous phase.
- Pick a horizon on peak amplitude of instantaneous amplitude volume. This step should generate very similar results as step 3 in workflow 1.
Section view below shows the picked horizon (orange line) overlay on the sstat header (red dots) generated from workflow1.
You can view the picked horizon TWT property in map view. This represents the time shift map based on peak amplitude.
- Use horizon amplitude extraction to extract the instantaneous phase volume attribute on the picked horizon. Disable the time slice and the phase shift attribute map will be displayed on the map view